dual system; double standard
Refers to a system or arrangement where two different standards, rules, or structures coexist, often with a critical nuance of inconsistency or unfairness.
That company has a dual salary system for regular employees and contract workers.
His words and actions seem to have a double standard.
Compound of 二本 (two, two long thin objects) and 建て (structure, system). The exact historical derivation is uncertain, but it likely originated from the idea of two pillars or frameworks supporting a single system.